Position feedback for sealed environments

ABSTRACT

A transport apparatus comprising a housing, a variable reluctance drive mounted to the housing, and at least one transport arm connected to the variable reluctance drive where the drive includes at least one rotor having salient poles of magnetic permeable material and disposed in an isolated environment, at least one stator having salient pole structures each defining a salient pole with corresponding coil units coiled around the respective salient pole structure and disposed outside the isolated environment where the at least one salient pole of the at least one stator and the at least one salient pole of the rotor form a closed magnetic flux circuit between the at least one rotor and the at least one stator, at least one seal partition configured to isolate the isolated environment; and at least one sensor including a magnetic sensor member connected to the housing, at least one sensor track connected to the at least one rotor, where the at least one seal partition is disposed between and separates the magnetic sensor member and the at least one sensor track so that the at least one sensor track is disposed in the isolated environment and the magnetic sensor member is disposed outside the isolated environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/540,058 filed Nov. 13, 2014 which is a non-provisional of and claimsthe benefit of U.S. provisional patent application No. 61/903,726 filedon Nov. 13, 2013, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

The exemplary embodiments generally relate to position feedback and,more particularly, to position feedback for sealed robotic drives.

2. Brief Description of Related Developments

Generally, existing direct drive technology, which for example usespermanent magnet motors or variable reluctance motors for actuation andoptical encoders for position sensing, exhibits considerable limitationswhen, for example, the magnets, bonded components, seals and corrosivematerials of the direct drive are exposed to ultra-high vacuum and/oraggressive and corrosive environments. To limit exposure of, forexample, the magnets, bonded components, electrical components, sealsand corrosive materials of the direct drive a “can-seal” is generallyused.

The can-seal generally isolates a motor rotor from a corresponding motorstator via a hermetically sealed non-magnetic wall or “can”, also knownas an “isolation wall”. Can-seals generally use a non-magnetic vacuumisolation wall that is located between the rotor and stator of a givenmotor actuator. As a result, the stator can be completely locatedoutside the sealed environment. This may allow for substantially cleanand reliable motor actuation implementations in applications such asvacuum robot drives used for semiconductor applications. However, thesensors or encoders may include electronic components that may belocated within the sealed environment where the electronic componentsmay be a potential contamination source and where the sealed environmentsubjected the electronic components to corrosion. As may be realized,hermetically sealed connectors are required for the electroniccomponents within the sealed environment so that wires or other signalcarrying medium can be routed through the isolation wall. As may berealized, these hermetically sealed connectors may be a potential leaksource. Further, in the case of optical sensors, contaminants orparticulates may be deposited on the feedback track (or scale) and canlead to signal degradation and sensor failure. In other aspects, windowsmay be provided through which the sensors operate however these windowsmay also be a source of leaks.

It would be advantageous to have a position feedback system that isoperative through an isolation wall between an isolated or otherwisesealed environment and an environment outside the sealed environmentsuch that the above-described issues are addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the disclosed embodiment areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIGS. 1A-1D are schematic illustrations of processing apparatusincorporating aspects of the disclosed embodiment;

FIGS. 2A-2D are schematic illustrations of portions of transportapparatus in accordance with aspects of the disclosed embodiment, andFIGS. 2E-2F are respectively cross-section perspective and enlargedcross-section illustrating further features;

FIGS. 2G-2K are schematic illustrations of a drive section in accordancewith aspects of the disclosed embodiment;

FIG. 3 is a schematic illustration of a portion of a position sensor inaccordance with aspects of the disclosed embodiment;

FIGS. 4A and 4B are schematic illustrations of portions of a sensor inaccordance with aspects of the disclosed embodiment;

FIGS. 5, 5A-1, and 5A-2 are schematic illustrations of a sensor inaccordance with aspects of the disclosed embodiment;

FIG. 5B is a flow chart in accordance with aspects of the disclosedembodiment;

FIG. 5C is a schematic illustration of a portion of a sensor inaccordance with aspects of the disclosed embodiment;

FIGS. 6A and 6C are schematic illustrations of a portion of a sensor inaccordance with aspects of the disclosed embodiment and FIG. 6Billustrates a position decoding algorithm in accordance with aspects ofthe disclosed embodiment;

FIGS. 7A-7D are schematic illustrations of a portion of a sensor inaccordance with aspects of the disclosed embodiment;

FIGS. 8A and 8B are schematic illustrations of a portion of a sensor inaccordance with aspects of the disclosed embodiment;

FIGS. 9A-9C are schematic illustrations of a portion of a sensor inaccordance with aspects of the disclosed embodiment;

FIG. 9D is a graph of an exemplary sensor output in accordance withaspects of the disclosed embodiment;

FIGS. 10A-10D are schematic illustrations of a portion of a sensor inaccordance with aspects of the disclosed embodiment; and

FIG. 11 is a schematic illustration of a sensor in accordance withaspects of the disclosed embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1A-1D, there are shown schematic views of substrateprocessing apparatus or tools incorporating the aspects of the disclosedembodiment as disclosed further herein. Although the aspects of thedisclosed embodiment will be described with reference to the drawings,it should be understood that the aspects of the disclosed embodiment canbe embodied in many forms. In addition, any suitable size, shape or typeof elements or materials could be used.

Referring to FIGS. 1A and 1B, a processing apparatus, such as forexample a semiconductor tool station 11090 is shown in accordance withan aspect of the disclosed embodiment. Although a semiconductor tool isshown in the drawings, the aspects of the disclosed embodiment describedherein can be applied to any tool station or application employingrobotic manipulators. In this example the tool 11090 is shown as acluster tool, however the aspects of the disclosed embodiment may beapplied to any suitable tool station such as, for example, a linear toolstation such as that shown in FIGS. 1C and 1D and described in U.S. Pat.No. 8,398,355, entitled “Linearly Distributed Semiconductor WorkpieceProcessing Tool,” issued Mar. 19, 2013, the disclosure of which isincorporated by reference herein in its entirety. The tool station 11090generally includes an atmospheric front end 11000, a vacuum load lock11010 and a vacuum back end 11020. In other aspects, the tool stationmay have any suitable configuration. The components of each of the frontend 11000, load lock 11010 and back end 11020 may be connected to acontroller 11091 which may be part of any suitable control architecturesuch as, for example, a clustered architecture control. The controlsystem may be a closed loop controller having a master controller,cluster controllers and autonomous remote controllers such as thosedisclosed in U.S. Pat. No. 7,904,182 entitled “Scalable Motion ControlSystem” issued on Mar. 8, 2011 the disclosure of which is incorporatedherein by reference in its entirety. In other aspects, any suitablecontroller and/or control system may be utilized.

In one aspect, the front end 11000 generally includes load port modules11005 and a mini-environment 11060 such as for example an equipmentfront end module (EFEM). The load port modules 11005 may be boxopener/loader to tool standard (BOLTS) interfaces that conform to SEMIstandards E15.1, E47.1, E62, E19.5 or E1.9 for 300 mm load ports, frontopening or bottom opening boxes/pods and cassettes. In other aspects,the load port modules may be configured as 200 mm wafer interfaces orany other suitable substrate interfaces such as for example larger orsmaller wafers or flat panels for flat panel displays. Although two loadport modules are shown in FIG. 1A, in other aspects any suitable numberof load port modules may be incorporated into the front end 11000. Theload port modules 11005 may be configured to receive substrate carriersor cassettes 11050 from an overhead transport system, automatic guidedvehicles, person guided vehicles, rail guided vehicles or from any othersuitable transport method. The load port modules 11005 may interfacewith the mini-environment 11060 through load ports 11040. The load ports11040 may allow the passage of substrates between the substratecassettes 11050 and the mini-environment 11060. The mini-environment11060 generally includes any suitable transfer robot 11013 which mayincorporate one or more aspects of the disclosed embodiment describedherein. In one aspect the robot 11013 may be a track mounted robot suchas that described in, for example, U.S. Pat. No. 6,002,840, thedisclosure of which is incorporated by reference herein in its entirety.The mini-environment 11060 may provide a controlled, clean zone forsubstrate transfer between multiple load port modules.

The vacuum load lock 11010 may be located between and connected to themini-environment 11060 and the back end 11020. It is noted that the termvacuum as used herein may denote a high vacuum such as 10⁻⁵ Torr orbelow in which the substrate are processed. The load lock 11010generally includes atmospheric and vacuum slot valves. The slot valvesmay provide the environmental isolation employed to evacuate the loadlock after loading a substrate from the atmospheric front end and tomaintain the vacuum in the transport chamber when venting the lock withan inert gas such as nitrogen. The load lock 11010 may also include analigner 11011 for aligning a fiducial of the substrate to a desiredposition for processing. In other aspects, the vacuum load lock may belocated in any suitable location of the processing apparatus and haveany suitable configuration.

The vacuum back end 11020 generally includes a transport chamber 11025,one or more processing station(s) 11030 and any suitable transfer robot11014 which may include one or more aspects of the disclosed embodimentsdescribed herein. The transfer robot 11014 will be described below andmay be located within the transport chamber 11025 to transportsubstrates between the load lock 11010 and the various processingstations 11030. The processing stations 11030 may operate on thesubstrates through various deposition, etching, or other types ofprocesses to form electrical circuitry or other desired structure on thesubstrates. Typical processes include but are not limited to thin filmprocesses that use a vacuum such as plasma etch or other etchingprocesses, chemical vapor deposition (CVD), plasma vapor deposition(PVD), implantation such as ion implantation, metrology, rapid thermalprocessing (RTP), dry strip atomic layer deposition (ALD),oxidation/diffusion, forming of nitrides, vacuum lithography, epitaxy(EPI), wire bonder and evaporation or other thin film processes that usevacuum pressures. The processing stations 11030 are connected to thetransport chamber 11025 to allow substrates to be passed from thetransport chamber 11025 to the processing stations 11030 and vice versa.

Referring now to FIG. 1C, a schematic plan view of a linear substrateprocessing system 2010 is shown where the tool interface section 2012 ismounted to a transport chamber module 3018 so that the interface section2012 is facing generally towards (e.g. inwards) but is offset from thelongitudinal axis X of the transport chamber 3018. The transport chambermodule 3018 may be extended in any suitable direction by attaching othertransport chamber modules 3018A, 3018I, 3018J to interfaces 2050, 2060,2070 as described in U.S. Pat. No. 8,398,355, previously incorporatedherein by reference. Each transport chamber module 3018, 3019A, 3018I,3018J includes any suitable substrate transport 2080, which may includeone or more aspects of the disclosed embodiment described herein, fortransporting substrates throughout the processing system 2010 and intoand out of, for example, processing modules PM. As may be realized, eachchamber module may be capable of holding an isolated or controlledatmosphere (e.g. N2, clean air, vacuum).

Referring to FIG. 1D, there is shown a schematic elevation view of anexemplary processing tool 410 such as may be taken along longitudinalaxis X of the linear transport chamber 416. In the aspect of thedisclosed embodiment shown in FIG. 1D, tool interface section 12 may berepresentatively connected to the transport chamber 416. In this aspect,interface section 12 may define one end of the tool transport chamber416. As seen in FIG. 1D, the transport chamber 416 may have anotherworkpiece entry/exit station 412 for example at an opposite end frominterface station 12. In other aspects, other entry/exit stations forinserting/removing workpieces from the transport chamber may beprovided. In one aspect, interface section 12 and entry/exit station 412may allow loading and unloading of workpieces from the tool. In otheraspects, workpieces may be loaded into the tool from one end and removedfrom the other end. In one aspect, the transport chamber 416 may haveone or more transfer chamber module(s) 18B, 18 i. Each chamber modulemay be capable of holding an isolated or controlled atmosphere (e.g. N2,clean air, vacuum). As noted before, the configuration/arrangement ofthe transport chamber modules 18B, 18 i, load lock modules 56A, 56B andworkpiece stations forming the transport chamber 416 shown in FIG. 1D ismerely exemplary, and in other aspects the transport chamber may havemore or fewer modules disposed in any desired modular arrangement. Inthe aspect shown, station 412 may be a load lock. In other aspects, aload lock module may be located between the end entry/exit station(similar to station 412) or the adjoining transport chamber module(similar to module 18 i) may be configured to operate as a load lock. Asalso noted before, transport chamber modules 18B, 18 i have one or morecorresponding transport apparatus 26B, 26 i, which may include one ormore aspects of the disclosed embodiment described herein, locatedtherein. The transport apparatus 26B, 26 i of the respective transportchamber modules 18B, 18 i may cooperate to provide the linearlydistributed workpiece transport system 420 in the transport chamber. Inthis aspect, the transport apparatus 26B may have a general SCARA armconfiguration (though in other aspects the transport arms may have anyother desired arrangement such as a frog-leg configuration, telescopicconfiguration, bi-symmetric configuration, etc.). In the aspect of thedisclosed embodiment shown in FIG. 1D, the arms of the transportapparatus 26B may be arranged to provide what may be referred to as fastswap arrangement allowing the transport to quickly swap wafers from apick/place location as will also be described in further detail below.The transport arm 26B may have a suitable drive section, such asdescribed below, for providing each arm with any suitable number ofdegrees of freedom (e.g. independent rotation about shoulder and elbowjoints with Z axis motion). As seen in FIG. 1D, in this aspect themodules 56A, 56, 30 i may be located interstitially between transferchamber modules 18B, 18 i and may define suitable processing modules,load lock(s), buffer station(s), metrology station(s) or any otherdesired station(s). For example the interstitial modules, such as loadlocks 56A, 56 and workpiece station 30 i, may each have stationaryworkpiece supports/shelves 56S, 56S1, 56S2, 30S1, 30S2 that maycooperate with the transport arms to effect transport or workpiecesthrough the length of the transport chamber along linear axis X of thetransport chamber. By way of example, workpiece(s) may be loaded intothe transport chamber 416 by interface section 12. The workpiece(s) maybe positioned on the support(s) of load lock module 56A with thetransport arm 15 of the interface section. The workpiece(s), in loadlock module 56A, may be moved between load lock module 56A and load lockmodule 56 by the transport arm 26B in module 18B, and in a similar andconsecutive manner between load lock 56 and workpiece station 30 i witharm 26 i (in module 18 i) and between station 30 i and station 412 witharm 26 i in module 18 i. This process may be reversed in whole or inpart to move the workpiece(s) in the opposite direction. Thus, in oneaspect, workpieces may be moved in any direction along axis X and to anyposition along the transport chamber and may be loaded to and unloadedfrom any desired module (processing or otherwise) communicating with thetransport chamber. In other aspects, interstitial transport chambermodules with static workpiece supports or shelves may not be providedbetween transport chamber modules 18B, 18 i. In such aspects, transportarms of adjoining transport chamber modules may pass off workpiecesdirectly from end effector or one transport arm to end effector ofanother transport arm to move the workpiece through the transportchamber. The processing station modules may operate on the substratesthrough various deposition, etching, or other types of processes to formelectrical circuitry or other desired structure on the substrates. Theprocessing station modules are connected to the transport chambermodules to allow substrates to be passed from the transport chamber tothe processing stations and vice versa. A suitable example of aprocessing tool with similar general features to the processingapparatus depicted in FIG. 1D is described in U.S. Pat. No. 8,398,355,previously incorporated by reference in its entirety.

Referring now to FIG. 2A, a schematic illustration of a portion of atransport apparatus drive 200 is illustrated. The transport drive may beemployed in any suitable atmospheric or vacuum robotic transport such asthose described above. The drive may include a drive housing 200H havingat least one drive shaft 201 at least partially disposed therein.Although one drive shaft is illustrated in FIG. 2A in other aspects thedrive may include any suitable number of drive shafts. The drive shaft201 may be mechanically suspended or magnetically suspended within thehousing 200H in any suitable manner. In this aspect the drive shaft issuspended within the housing with any suitable bearings 200B but inother aspects the drive shaft may be magnetically suspended (e.g. aself-bearing drive) in a manner substantially similar to that describedin U.S. Pat. No. 8,283,813 entitled “Robot Drive with Magnetic SpindleBearings” issued on Oct. 9, 2012, the disclosure of which isincorporated by reference herein in its entirety. Each drive shaft ofthe drive 200 may be driven by a respective motor 206 where each motorincludes stator 206S and a rotor 206R. The exemplary embodiment depictedin the figures has what may be referred to as a rotary driveconfiguration that is illustrated for purposes of facilitatingdescription and features of the various aspects, as shown and describedherein. As may be realized the features of the various aspectsillustrated with respect to the rotary drive configuration are equallyapplicable to a linear drive configuration. It is noted that the drivemotors described herein may be permanent magnet motors, variablereluctance motors (having at least one salient pole with correspondingcoil units and at least one respective rotor having at least one salientpole of magnetic permeable material), or any other suitable drivemotors. The stator(s) 206S may be fixed at least partly within thehousing and the rotor(s) 206R may be fixed in any suitable manner to arespective drive shaft 201. In one aspect, the stator(s) 206S may belocated in an “external” or “non-sealed” environment that is sealed froman atmosphere in which the robot arm(s) 208 operate (the atmosphere inwhich the robot arm(s) operate is referred to herein as a “sealed”environment which may be a vacuum or any other suitable environment)through the employment of an isolation wall or barrier while therotor(s) 206R is located within the sealed environment in a mannersubstantially similar to that described in U.S. provisional patenthaving U.S. application Ser. No. 61/903,813 entitled “SEALED ROBOTDRIVE” and filed on Nov. 13, 2013, the disclosure of which isincorporated by reference herein in its entirety and as will bedescribed in greater detail below. It is noted that the termsnon-ferromagnetic separation wall, seal partition or isolation wall(which will be described in greater detail below) as used herein referto a wall made of any suitable non-ferromagnetic material that may bedisposed between the moving parts of the robot drive and/or sensor andthe corresponding stationary parts of the robot drive and/or sensor.

In one aspect the housing 200H of the drive 200 has a substantially drumshaped configuration (e.g. a drum structure) having an exterior 200HEand an interior 200HI. The housing 200H, in one aspect, is an unitaryone piece monolithic structure while, in other aspects, the housing 200His an integral assembly having two or more hoops fastened together inany suitable manner so as to form the drum structure of the housing200H. The interior 200HI of the housing includes a stator interfacesurface 200HS in which the stator 206S of the variable reluctance motor206 is located. The stator interface surface 200HS (and hence thehousing 200H) is configured to provide rigidity and support for thestator 206S. As may be realized, the stator interface surface 200HS (andhence the housing 200H) is a datum surface that positions the stator206S (and isolation wall 204 which in one aspect is supported by thestator so that the stator is located in an atmospheric environmentseparate from the vacuum environment in which the rotor is located) tocontrol a gap between the stator 206S and rotor 206R. The housing 200Halso includes a rotor interface surface 200HR that interfaces with andpositions the rotor 206R (e.g. the bearings 200B are positioned on thedrive shaft 201/rotor 206R in a predetermined position and the bearings200B interface with the rotor interface surface 200HR) so that the rotor206R is positioned in a predetermined position relative to the stator206S. As may be realized, the stator interface surface 200HS is a datumsurface for the rotor interface surface 200HR (and hence the rotor206R/drive shaft 201) so that the rotor 206R (and drive shaft 201connected thereto) and the stator 206S are positioned relative to anddepend from a common datum formed by the housing 200H. In one aspect thehousing 200H includes a control board aperture or slot PCBS formed inthe housing 200H and into which one or more printed circuit boards PCB(similar to PCB 310 described below which include sensor 203 thatinterfaces with the sensor or encoder track 202 described below) locatedin the atmospheric environment and separated from the sensor track 202(which is located in the vacuum environment) by a vacuum barrier in amanner similar to that described below. The control board aperture PCBSincludes a sensor interface surface 200HT that positions the sensor 203relative to the stator interface surface 200HS (e.g. the common datum ofthe housing 200H) in a predetermined position. As may be realized, thesensor track 202 is connected to the rotor 206R so that the sensor track202 is located in a predetermined location relative to the rotorinterface surface 200HR. As such, the relative positioning of the sensorinterface surface 200HT and the rotor interface surface 200HR with thestator interface surface 200HS positions and controls the gap betweenthe sensor 203 and the sensor track 202 where the stator 206S, the rotor206R, the sensor 203 and the sensor track 202 are positioned relative toand dependent from the common datum. In one aspect, the housing 200Hincludes any suitable slot or aperture MLS through which any suitabledrive connectors CON pass for providing power and control signals to(and feedback signals from) the drive 200.

Referring to FIG. 2K, it should be understood that while FIGS. 2G-2Jillustrate a drive having a single drive shaft 201 for exemplarypurposes only, in other aspects the drive includes any suitable numberof motors having any suitable corresponding number of drive shafts. Forexample, FIG. 2K illustrates a drive 200″ having two motors 206A, 206Barranged in a stacked or in-line configuration. Here each motor 206A,206B includes a respective housing 200H (substantially similar to thatdescribed above) where the housings are connected to each other in anysuitable manner to form the multiple motor (e.g. multiple degree offreedom) drive 200″ so that a drive shaft 201 of motor 206B extendsthrough an aperture in a drive shaft 201A of motor 206A to form acoaxial drive spindle.

Referring also to FIG. 2B, a transport apparatus drive 200′substantially similar to drive 200 is illustrated having a coaxial driveshaft arrangement with two drive shafts 201, 210. In this aspect thedrive shaft 201 is driven by motor 206 (having stator 206S and rotor206R) while shaft 210 is driven by motor 216 (having stator 216S androtor 216R). Here the motors are shown in a stacked arrangement (e.g. inline and arranged one above or one in front of the other). However, itshould be understood that the motors 206, 216 may have any suitablearrangement such as a side by side or concentric arrangement. Forexample, referring to FIG. 2D, in one aspect the substrate transportapparatus 100 is shown as having a low profile planar or “pancake” stylerobot drive configuration where the motors are concentrically nestedwithin each other in a manner substantially similar to that described inU.S. Pat. No. 8,008,884 entitled “Substrate Processing Apparatus withMotors Integral to Chamber Walls” issued on Aug. 30, 2011 and U.S. Pat.No. 8,283,813 entitled “Robot Drive with Magnetic Spindle Bearings”issued on Oct. 9, 2012, the disclosures of which are incorporated byreference herein in their entireties. The substrate transport apparatus100 may include a reluctance drive 100D having one or more stators andcorresponding rotors (which in this aspect include an outer rotor 101and an inner rotor 102). The rotors 101, 102 may be actuated by theirrespective stators through an enclosure or isolation wall 103 based onany suitable reluctance motor principle. It is noted that due to, forexample, the comparatively large rotor diameters and high torquecapabilities the pancake style drive configurations may offer a directdrive alternative to harmonic drive robots for high/heavy payloadapplications. In other aspects any suitable harmonic drive may becoupled to an output of the motors described herein for driving one ormore robotic arms. The pancake style drive configurations may also allowfor a hollow central drive section which can accommodate a vacuum pumpinlet and/or support partial or full integration of vacuum pumpingarrangement within the robot drive, such as in compact vacuum chamberswith limited space around the robot drive or any other suitable chamberin which the robot drive is at least partially disposed.

The drives described herein may carry any suitable robot arm 104 (asnoted above) configured to transport, for example, semiconductor wafers,flat panels for flat panel displays, solar panels, reticles or any othersuitable payload. In this aspect the robot arm 104 is illustrated as abi-symmetric type robot arm (e.g. having opposing end effectors that arelinked in extension and retraction) where one of the upper arms 104U1,104U1′ is attached to the outer rotor 101 and the other upper arm 104U2,104U2″ is attached to the inner rotor 102. In other aspects, anysuitable number and type of robot arms may be attached to the drivemotor arrangements described herein. In addition to the bi-symmetric arm104 other examples of arm configurations that may be employed with thepancake type motor arrangements or the stacked motor arrangementsinclude, but are not limited to, the arm configurations described inU.S. patent application Ser. No. 12/117,415 entitled “SubstrateTransport Apparatus with Multiple Movable Arms Utilizing a MechanicalSwitch Mechanism” filed on May 8, 2008, the disclosure of which isincorporated by reference herein in its entirety. For example, the armsmay be derived from a conventional SCARA (selective compliantarticulated robot arm)-type design, which includes an upper arm, aband-driven forearm and a band-constrained end-effector, by eliminatingthe upper arm, a telescoping arm or any other suitable arm design.

The operation of the arms may be independent from each other (e.g. theextension/retraction of each arm is independent from other arms), may beoperated through a lost motion switch or may be operably linked in anysuitable way such that the arms share at least one common drive axis. Asan example, a radial extension move of the either end effector 104E1,104E2 of the bi-symmetric arm can be performed by substantiallysimultaneously rotating the outer rotor 101 and inner rotor 102 inopposite directions substantially at the same rate. Rotation of the arm104 as a unit can be performed by rotating the outer rotor 101 and innerrotor 102 in the same direction as substantially the same rate.

Referring again to FIGS. 2A and 2B and also to FIG. 2C, each drive shaft201 may also have mounted thereto a sensor or encoder track 202 with aposition determining indicia or features that interface with a sensor203. It is noted that the sensors described herein may be configuredsuch that the read head portion of the sensor 203 (e.g. the portion ofthe sensor to which a sensing member is mounted) are modules that can beinserted and removed from the drive housing or isolation wall 204 (it isnoted that the isolation wall 204 may be a common isolation wall thatalso seals the drive stators from the sealed environment). The sensor203 may be fixed at least partly within the housing 200H in any suitablemanner that allows sensing elements or members 203H of the sensor 203 toread or otherwise be influenced by one or more scales 202S (which willbe described below) for providing position signals to any suitablecontroller such as motion controller 190 (which may be substantiallysimilar to controller 11091 described above). In one aspect at least aportion of the sensor 203 may be located in the external environment andsealed or otherwise isolated from the sealed environment with theisolation wall 204 as will be described in greater detail below so thatthe sensor electronics and/or magnets are disposed in the externalenvironment while the sensor track is disposed in the sealedenvironment. The sealed environment may be difficult to monitor directlydue to, for example, harsh environmental conditions, such as vacuumenvironments or environments with extreme temperatures. The aspects ofthe disclosed embodiments described herein provide non-intrusiveposition measurement of a moving object (e.g. such as a motor rotor, arobot arm connected to the motor or any other suitable object) withinthe sealed environment.

In one aspect, referring to FIG. 3, the sensor 203 may utilize magneticcircuit principles to detect the position of the encoder track 202 wherethe encoder track has at least one encoder scale (e.g. where each of theat least one encoder scale has a predetermined pitch that may bedifferent than a pitch of other ones of the at least one encoder scale)located within the sealed environment. The magnetic sensing systemillustrated in FIG. 3 is shown in a representative manner and may beconfigured as a Giant Magneto Resistive sensor (GMR) or as adifferential type GMR (i.e. that senses the gradient field differentialbetween several locations, otherwise referred to as a gradiometer) aswill be described below. The sensor may include at least one magnetic orferromagnetic source 300, the ferromagnetic encoder track 202, and atleast one magnetic sensing element or member 203H (corresponding to eachmagnetic source) disposed substantially between the magnetic source andthe ferromagnetic track.

The encoder track may be configured so that the track width (e.g. trackface with encoding features thereon) may extend in a plane extendingradially outwards with the position encoding features varyingorthogonally from the track plane (e.g. up and down) as depicted in FIG.2A. In other aspects, the track width may be disposed in an axialdirection parallel to the drive axis (e.g. in a rotary driveconfiguration the track face forms an annulus or cylinder surroundingthe drive axis T as in a “drum” shape, for example tracks 202S1′,202S2′, 202S3′, FIGS. 2E-F) with the encoding features projectingradially (for a rotary drive) or laterally from the track plane. In thisaspect the at least one magnetic sensing member 203H may have asubstantially flat (or otherwise without depending features) trackinterface that interfaces substantially directly with the track 202 butin other aspects, as described below, the at least one magnetic sensormay be connected to ferromagnetic members that include ferromagneticfeatures that interface with corresponding features on the track. In oneaspect the magnetic source and the at least one sensing member 203H maybe mounted to or otherwise integrally formed on a printed circuit board(PCB) 310 where the printed circuit board is a common circuit board(e.g. common to each magnetic source and each of the at least onesensing member). In other aspects each magnetic source and sensingmember may be mounted to one or more respective printed circuit boards.In one aspect the magnetic source 300 may be a permanent magnet locatedwithin the external environment. In other aspects the magnetic source300 may be any suitable source such as coils configured to be energizedto produce a magnetic field. In one aspect the magnetic field generatedby the magnetic source (the field lines illustrated in FIG. 3 forexample purposes) depart from a north pole N (e.g. pole facing away fromthe track, in other aspects the magnetic poles may have any suitableorientations) of the source 300 (or in the case of energized coils in adirection determined by the flow of current through the coils), maypropagate as shown, crossing the PCB 310, and flowing across the gap(e.g. between the sensing member 203H and the track 202) through thenon-ferrous isolation wall 204, to the ferromagnetic track 202 and backto the opposing pole S of the magnetic source 300. As the ferromagnetictrack moves relative to the magnetic source 300 one or more magneticfield profiles are generated. The magnetic field profiles may have ageneral shape of one or more of a sine wave or a cosine wave. Thesensing member 203H is configured to detect changes to the magnetic fluxthat correlate with the ferromagnetic track motion (e.g. the magneticfield profiles).

In one aspect the sensing member(s) 203H may be any suitable giantmagneto resistive (GMR) sensing element/member capable of sensing amagnetic field in one or more locations. In other aspects the sensingmember(s) may be any suitable sensing elements capable of sensing amagnetic field. In one aspect the sensing member 203H may be configuredto produce a sinusoidal signal that can be used to provide a phase angleassociated with, for example, an incremental (and/or absolute) positionof the ferromagnetic track 202. In another aspect, referring to FIGS. 4Aand 4B the sensing member(s) may be a differentialGiant-Magneto-Resistive (GMR) sensing member (e.g. gradiometer) that isconfigured to sense a gradient field between two locations in space. Themagnetic sensing system may be a gradiometer as previously noted. In thegradiometer configuration, an analog output signal of each sensingmember may be proportional to the magnetic field gradient between twopoints in space. FIG. 4A illustrates a representative gradiometersensing member 203H′ including magneto resistive elements MRE that maybe arranged to form, for example, a Wheatstone bridge that may effect adifferential encoder channel. As may be realized, the arrangement of theMRE's (e.g. R1-R4) on the gradiometer sensing member may becharacteristic of the encoding features on the encoder track andmagnetic source. FIG. 4B illustrates an exemplary gradiometer sensingmember 203H″ in accordance with another aspect of the disclosedembodiment including magneto resistive elements MRE arranged to providetwo differential signals (e.g. sine/cosine). The track pitch P (FIG. 3)and a position of the magneto resistive elements MRE on the sensingmember 203H, 203H′, 203H″ may be matched such that differential sine andcosine outputs are obtained from each of the sensing members 203H,203H′, 203H″.

Referring to FIG. 5, there is shown a schematic diagram of the driveposition determining circuitry in accordance with an aspect of thedisclosed embodiment. The position determining circuitry may beintegrated to a single printed circuit board, or otherwise packaged asdesired. In one aspect the printed circuit board 310 (see FIG. 5) mayinclude the one or more sensing members 503H (substantially similar toone or more of sensing members 203H, 203H′, 203H″ described above whichmay be integrated on a single chip), an error compensation unit 506, asignal conditioning unit 501, a data sampling unit 502, a decoding unit507, a broadcasting unit 504 and a control and synchronization unit 505(referred to herein as the “control unit”). The functional units areshown and described separately for simplicity but may be arranged andcombined in the circuitry as desired. In other aspects the printedcircuit board 310 may have any suitable configuration for carrying outposition sensing as described herein.

The control and synchronization unit 505 may include any suitablemodules for performing the sensor functions described herein. Forexample, referring also to FIG. 5C, the control and synchronization unit505 may include one or more analog to digital converter modules 505A(oversampling), 505E (quiet time), 505F (tracks), an absolute positiondecoding module 505B, a sensor hysteresis compensation module 505C, atemperature compensation module 505D, an automatic track alignmentcalibration module 505G, an output protocol module 505H and an automaticamplitude, offset and phase calibration module 505I. As may be realized,while the modules 505A-505I are described as being integrated with thecontrol and synchronization unit 505 in other aspects the modules505A-505I may be mounted to or integrated in the circuit board 310 so asto be accessible by the control and synchronization unit 505. Forexample, the modules 505A-505I may be integrated into one or more of thefunctional units 501, 502, 504, 503, 507 or any other suitable componentof the circuit board 310 sensing circuit. In still other aspects themodules 505A-505I may be mounted “off board” the circuit board 310 suchas in any suitable controller but accessible by the control andsynchronization unit 505. The oversampling analog to digital convertermodule 505A may be configured to oversample (at any desired configurablesampling rate) sensor readings as described herein to improve noiseimmunity. The analog to digital converter module 505E may be configuredto sample sensor signals at “quiet times” as described herein to avoidnoisy events within the sensor circuit. The analog to digital convertermodule 505F may be configured to provide an on board analog to digitalconversion of track data (e.g. position feedback data) and allow forimproved signal integrity while avoiding a need for long interconnectcables between the position feedback and an external controller. Theabsolute position decoding module 505B may be configured to allow theabsolute position of the sensor to be identified upon power up or at anyother desired time such that an incremental position can be properlyaligned to the true absolute position. The sensor hysteresiscompensation module 505C may be configured to minimize hysteresisinherent to the sensors 503H at any suitable positions corresponding toone or more of a motor position or a robot arm position. The temperaturecompensation module 505D may be configured to allow compensation oftemperature effects and may include any suitable temperature look uptable. The automatic track alignment calibration module 505G may beconfigured to identify a common origin between different tracks 202using, for example, a software calibration so relax tolerances of sensorlocations in the circuit board 310 relative to the respective tracks202. The output protocol module 505H may be configured to provide asubstantially universal integration with different types of controllersusing different communication protocols.

As may be realized, the one or more sensing members 503H may generateraw analog signals (sine and/or cosine signals) that reflect thetopology of a respective scale 202S on the ferromagnetic track 202 (FIG.2C). The error compensation unit 506 may be configured to suitablyaddress any limitations corresponding to the sensing technology selected(which in this case may be GMR sensing technology or any other suitablesensing technology). Examples of such limitations may include signaldistortion due to sensor non-linearity and saturation as well astemperature drift effects and external magnetic field disturbances. Theerror compensation may be performed on demand such as with commands fromthe control and synchronization unit 505 to the error compensation unit506 or at any other suitable predetermined time(s). The signalconditioning unit 501 may be configured to scale (or otherwisecalibrate—an example of which is the normalization of the sinusoidalamplitudes and offset removal) the raw analog signals from the sensingmembers 503H to a value within a deterministic range. The data samplingunit 502 may be any suitable converter, such as an analog to digitalconverter, configured to convert the conditioned signals into rawdigital data to be processed by any suitable controller, such as thosedescribed herein. The decoding unit 503 may be configured to process theraw digital data generated by the data sampling unit 502 and convertthat raw digital data to position output data. It is noted that if anabsolute position is desired, the absolute position may be obtained fromanalyzing data from multiple scales 202S on the ferromagnetic track 202as will be described below. The broadcasting unit 504 may be configuredto transmit the position output data to an external device such as anysuitable motion controller 190 (which may be communicably connected tothe at least one sensor where the a control and synchronization unit 505receives sensor signals from the at least one sensor and is suitablyconfigured to control a change in at least a predeterminedcharacteristic of the sensor signals, such as those noted below, inresponse to communications from the motion controller). The broadcastingunit 504 may also be configured to provide input information from themotion controller 190 that may be used by the control andsynchronization unit 505 to effect timing and scheduling as will bedescribed below.

The control and synchronization unit 505 may be configured to manage andschedule the individual functional units 503H, 501, 502, 504, 506, 507as shown in FIG. 5. As noted above, the individual functional units503H, 501, 502, 504, 506, 507 and control and synchronization unit 505may be integrated into a single position feedback module that can beinstalled in and removed from, for example, any suitable motor as unitor unitary module. In one aspect the position feedback module may becalibrated (FIG. 5B, Block 589) in any suitable manner. For example, thecalibration may be performed “off board” a motor (e.g. while notinstalled in a motor) on, for example, at test bench as the relationshipbetween the sensing units is known. For example, any suitable softwarecalibration may be performed such that the position feedback module iscalibrated off board in its entirety (e.g. such that the module is readyfor operation) and installed. A final alignment calibration between thesensing unit(s) 503H and the respective tracks 202 may be performed(such as automatically with the on-board automatic track calibrationmodule 505G) with the position feedback module in place (e.g. on boardthe motor). In other aspects the motion controller 190 may be configuredto manage and schedule the individual functional units 503H, 501, 502,504, 506, 507 in a manner substantially similar to that described belowwith respect to the control and synchronization unit 505. In still otheraspects the management and scheduling of the individual functional unitsmay be shared between the control and synchronization unit 505 and themotion controller 190. For example, the error compensation unit 506 canbe enabled by the control and synchronization unit 505 at any suitabletime (e.g. such as on-demand) to improve accuracy and reproducibility ofthe sensing member 503H signal output. The signal conditioning unit 501may also be controlled by the control and synchronization unit 505 tosubstantially automatically normalize the analog signals upon requestfrom the control and synchronization unit 505 or at any other suitabletime. The data sampling unit execution can also be controlled by thecontrol and synchronization unit 505 so that position data is sampled at“quiet” times where the sensing circuit is not subject to transients orat any other suitable time(s). The control and synchronization unit 505may also be configured to define oversampling parameters to improve dataquality from the data sampling unit 502. The oversampling data may betaken at any suitable time such as during “quiet times” as describedherein. The control and synchronization unit 505 may also effectposition calculations by sending command(s) to the decoding unit 507when proper sampled data is available. The control and synchronizationunit 505 may also be configured to control the broadcasting unit 504such that a final decoded position is output at predetermined times.

An exemplary implementation of the block diagram of FIG. 5 isillustrated in FIG. 5A. In this aspect the printed circuit board 310includes three sensing members 503H1, 503H2, 503H3 (each capable ofproviding two differential signals) for obtaining position signals froma ferromagnetic track 202 (see for example, FIGS. 2C and 6A) havingthree scales 202S. In one aspect the sensing members 503H1, 503H2, 503H3(as well as the other sensors described herein) may be immovably fixedto the circuit board. In other aspects the sensing members (as well asthe other sensors described herein) may be movably mounted to thecircuit board so that the sensing members may be adjusted relative totheir respective track 202 scales 202S. Referring to FIGS. 2C and 6A-6C,in one aspect the scales 202S may represent a 3-scale Nonius patternthat includes a master scale 202S1, a Nonius scale 202S2 and a segmentscale 202S3 but in other aspects the ferromagnetic track may include anysuitable number of scales having any suitable positional relationshiprelative to one another. Here each scale 2102S may include A respectiveequally spaced pattern (e.g. each scale pattern may have a respectivepitch P1, P2, P3) of ferromagnetic features 202SE (e.g. slots,protrusions, etc.). For each scale 202S there may be a dedicated sensingmember 503H1-503H3 that is configured to provide analog signal outputsthat substantially mimic, for example, sine and cosine waves. In oneaspect one or more of the sensing members 503H1-503H3 may be arranged atany suitable angle α1, α2 relative to another of the sensing members503H1-503H3 and/or a respective track 202S1-202S3. In other aspects thesensing members 503H1-503H3 may have any suitable position relationshiprelative to each other and/or the respective tracks 202S1-202S3. As maybe realized, each scale period and number of ferromagnetic features202SE allows for a track design that can be used to decode the absoluteposition of the track by using any suitable Nonius interpolationapproach (see FIG. 5 which illustrates one suitable absolute positiondecoding algorithm for a 3-scale track 202 as described herein).

One or more coils 600 may be integrally formed as a one piece unit with(or otherwise mounted to or formed on) the printed circuit board 310 inany suitable manner for hysteresis compensation as will be describedbelow. It is noted that the data sampling unit 502 and decoding unit 507may be formed as an integral device or module as shown in FIG. 5A whilein other aspects the data sampling unit 502 and decoding unit 507 may beseparate units. As can also be seen in FIG. 5A any suitable memory 505Mmay be connected to the control and synchronization unit 505.

In one aspect the control and synchronization unit 505 may be configuredto generate sensor signal commands to at least one sensor based onsensor signals received from the at least one sensor, where the sensorsignal commands effect a change in at least a predeterminedcharacteristic of the sensor signals. For example, the control andsynchronization unit 505 may be configured to control hysteresis in anysuitable manner, such as through a hysteresis compensation mechanism ormodule 505C (e.g. the one or more coils 600 and associated hardware andsoftware for energizing the coil(s)) as will be described below. In oneaspect the control and synchronization unit 505 may effect energizingthe coils so that the respective sensing members 503H1, 503H2, 503H3 aredriven into saturation. The control and synchronization unit 505 mayschedule position data sampling times, such as with module 505E, so thatposition data is not sampled during the times that the hysteresis isbeing compensated (e.g. position data is not sampled when the coil(s) isenergized). By compensating for hysteresis in the sensing members 503H,consistent analog signals may be output by the sensing members 503H. Inone aspect the one or more coils 600 may be provided on the printedcircuit board 310 adjacent a respective sensing member 503H1, 503H2,503H3 as shown in FIGS. 7A-7D which illustrate the coil(s) 600 beingformed in one or more layers 630-635 on or in the printed circuit board310. As an example of hysteresis compensation in accordance with aspectsof the disclosed embodiment, the control and synchronization unit 505may cause the application of a hysteresis compensation field in the oneor more of the sensing members 503H by energizing the coil(s) 600 at anysuitable time (FIG. 5B, Block 590). For example, in one aspect, thecontrol and synchronization unit 505 may monitor the signals receivedfrom the sensors and when a predetermined characteristic of the signal(e.g. noise, amplitude, signal distortion, etc.) is outside apredetermined range and/or exceeds a threshold value the hysteresiscompensation field may be generated. The control and synchronizationunit 505 may wait a predetermined time after the hysteresis compensationfield collapses and then command the signal conditioning unit 501 toapply an appropriate (e.g. any suitable) signal compensation to theresulting hysteresis-compensated signal from one or more of the one ormore sensing members 503H (FIG. 5B, Block 591). It is noted thatposition signals from the one or more sensing members 503H may not bevalid during times where the coil(s) 600 are energized and thehysteresis compensation field is not collapsed. The control andsynchronization unit 505 may trigger or otherwise command the datasampling unit 502 to convert the conditioned analog signal into digitaldata (FIG. 5B, Block 592) and command the decoding unit 507 to collectthe digital data from the data sampling unit 502 and translate thisdigital data into final corrected position data (FIG. 5B, Block 593).The control and synchronization unit 505 may command the broadcastingunit 504 to communicate the final corrected position data to anysuitable controller such as controller 190 (FIG. 5B, Block 594) suchthat the controller 190 uses the final corrected position data tocontrol movement of the robot drive 200 and the one or more armsattached thereto.

The aspects of the disclosed embodiment may allow for a level ofcustomization that can be used to optimize the performance of anysuitable position feedback system such as those described herein withrespect to semiconductor automation robots. In one aspect the controland synchronization unit 505 and/or the data sampling unit 502 may beconfigured such that the analog to digital conversion is configurablewith oversampling (such as with module 505A) to allow for improved noiseimmunity. As noted above, the data sampling and analog to digitalconversion of the sensor signals for determining the position of, e.g.,the drive 200 (and hence the robot arms) may be performed at “quiettimes” (such as with modules 505A and/or 505E) which, as noted above,are times that avoid noisy events within the circuit (e.g. noisy eventssuch as hysteresis compensation, transients, etc.). In another aspectsthe control and synchronization unit 505 may include any suitableprogramming and/or algorithms stored in, for example, memory 505M thatallows for on-demand absolute position decoding (such as with module505B) where the absolute position can be identified upon power up or anyother suitable time such that an incremental position can be properlyaligned to the absolute position (this can be effected through thedifferent scales on the ferromagnetic track as described herein). Thecontrol and synchronization unit 505 may include any suitableprogramming and/or algorithms stored in, for example, memory 505M thatallows for on-board (e.g. determined locally by the processingcapabilities of the sensor 203) substantially automatic track alignmentcalibration (such as with module 505G) where a common origin between thedifferent scales 202S of the ferromagnetic track 202 is identified (e.g.such as by comparing signals of each scale) so that tolerances of thesensor member 503H locations can be relaxed in the electrical circuit ofthe printed circuit board 310 relative to the ferromagnetic track 202.As noted above, the coil(s) 600 and the control and synchronization unit505 may allow for on-demand hysteresis compensation (as noted above—suchas with module 505C) that may be inherent to some sensing members at anysuitable positions of the ferromagnetic track (and hence the robotdrive/robot arm) where repeatability of position is desired. The controland synchronization unit 505 may include any suitable programming and/oralgorithms stored in, for example, memory 505M that allows for on-boardsubstantially automatic amplitude, offset and phase calibration (such aswith module 505I) which may allow for substantially real-time (wherereal time refers to an operational deadline from an event to a systemresponse) signal conditioning to compensate for drifts due to, forexample, mechanical run out (or other state condition of the sensor suchas a rotation direction of the track 202 and/or sensor hysteresis)and/or ambient condition effects (e.g. such as a temperature of the atleast one sensor). In another aspect, the control and synchronizationunit 505 may include any suitable programming and/or algorithms storedin, for example, memory 505M that allows for on-board temperaturecompensation (such as with module 505D). For example, the sensor 203 mayinclude a temperature sensor 520 (FIG. 5A) communicably connected to thecontrol and synchronization unit 505 for determining a temperature ofone or more of the printed circuit board 310, the sensing members 203H,203H′, 203H″, 503H1-503H3, the ferromagnetic track 202 (and/or scalesthereon) or any other suitable component of the sensor 203. Any suitablelookup table may be resident in any suitable memory, such as memory 505Mthat correlates, for example, sensor signals with temperature to providesignal conditioning compensation against temperature effects. As can beseen in FIG. 5A, the sensor may be provided with on-board analog todigital conversion for each scale 202S of the ferromagnetic track 202which may allow for increased analog signal integrity and avoid a needfor long interconnect cables between the position feedback sensor 203and an external controller such as controller 190. The control andsynchronization unit 505 and/or the broadcast unit 504 may also beconfigured to provide multiple output protocols (such as with module505H) to allow for substantially universal integration with differenttypes of controllers. For example, the different communication protocolsmay be stored in any suitable memory of the sensor, such as memory 505Mor a memory resident in the broadcast unit 504.

Referring now to FIGS. 8A and 8B, a portion of a sensor 203′ isillustrated in accordance with an aspect of the disclosed embodiment.The sensor 203′ may be substantially similar to those described abovehowever, in this aspect the sensing member 803H (which may besubstantially similar to the sensing members described above) may bedisposed substantially within a sensor air gap 810 of a ferromagneticcircuit member or flux loop 820. The ferromagnetic circuit member 820may include a magnetic source 300 (which may be a permanent magnet orone or more coils configured to generate a magnetic field as describedabove), a first leg 822 (which includes the sensor air gap 810) coupledto the magnetic source 300, a first extension member 823 communicablyconnected to the first leg 822 such that the isolation wall 204 isdisposed between the first extension member and the first leg (in otheraspects the first leg and first extension member may be a one piecemember that extends through the isolation wall 204 in any suitablemanner), a second extension member 824 communicably interfaced with thefirst extension member 823 across a sensor track air gap 830, and asecond leg 825 communicably connected to the second extension 824 suchthat the isolation wall 204 is disposed between the second extensionmember and the second leg (in other aspects the first leg and firstextension member may be a one piece member that extends through theisolation wall 204 in any suitable manner). The second leg 825 is alsocoupled to the magnetic source 300. As can be seen in FIG. 8A, theferromagnetic circuit member 820 forms a magnetic circuit between themagnetic source 300 and the track 202 such that magnetic flux departsfrom, for example, a north pole of the magnetic source 300, travelsalong the first leg 822, across the sensor air gap 810 where the sensoris located, across the non-ferromagnetic isolation wall 204, continuingalong the first extension member 823 across the track air gap 830 (e.g.through the track 202) and along the second extension member 823 toreturn through the isolation wall 204 such that the magnetic fluxtravels along the second leg 825 to, for example, the south pole of themagnetic source 300. The arrangement of the ferromagnetic circuit member820 allows the sensing member 803H to detect changes in the sensor airgap 810 reluctance caused by changes in the profile of the track 202(e.g. as the track 202 moves relative to the extension members 823, 824)without having to be placed in an air gap located between the track 202and the magnetic source 300. The arrangement of the ferromagneticcircuit member 820 also allows for the sensor electronics to be locatedin the external environment as noted above. It is noted that theisolation wall may be disposed between the portions of the ferromagneticcircuit members in a manner substantially similar to that described inU.S. provisional patent having U.S. application Ser. No. 61/903,813entitled “SEALED ROBOT DRIVE” and filed on Nov. 13, 2013, previouslyincorporated by reference herein in its entirety.

Referring now to FIGS. 9A-9C, a portion of a sensor 203″ is illustratedin accordance with an aspect of the disclosed embodiment. The sensor203″ may be substantially similar to those described above however, inthis aspect the sensing member 803H (which may be substantially similarto the sensing members described above) may be disposed substantiallywithin a sensor air gap 905 of a ferromagnetic bridge circuit 901 thatis configured to emulate a Wheatstone bridge. The ferromagnetic bridgecircuit includes a first the ferromagnetic circuit member 910 and asecond the ferromagnetic circuit member 911 both of which may besubstantially similar to the ferromagnetic circuit member 820 describedabove such that each of the first and second the ferromagnetic circuitmembers 910, 911 have portions (e.g. separated by the isolation wall204) that are located in the external environment and in the sealedenvironment. Each of the ferromagnetic circuit members 910, 911 have twoair gaps (e.g. one disposed on either side of the isolation wall 204).For example, ferromagnetic circuit member 910 includes air gap CR2disposed in the external environment and CR1 disposed in the sealedenvironment while ferromagnetic circuit member 911 includes air gap CR3disposed in the external environment and air gap VR disposed in thesealed environment. It is noted that the magnets 300 of each of theferromagnetic circuit members 910, 911 are also disposed in the externalenvironment in a manner substantially similar to that described abovewith respect to FIGS. 8A and 8B. The air gaps CR1-CR3 may be constantreluctance air gaps. The air gap VR may be a variable reluctance air gapwhere the variable reluctance is caused by one or more scales of thetrack 202 (which is located within the air gap VR). A bridge member BRcommunicably connects the ferromagnetic circuit members 910, 911 to eachother and includes a sensor air gap 905 in which the sensing member 803His at least partially disposed. In operation the ferromagnetic bridgecircuit 901 is substantially balanced whenever the air gap CR1-CR3, VRreluctances are substantially equal to each other. In the case where theferromagnetic bridge circuit 901 is balanced the sensing member 803Hdoes not detect a change in magnetic flux (or does not detect a magneticflux) across the sensor air gap 905. The reluctance balance is disturbedby the motion of the track 202 scale(s) through the air gap VR. Forexample, in the case of a rotary track 202 (or in other aspects a lineartrack), as the track 202 moves the magnetic flux changes across thesensor air gap 905. The sensing member 803H senses or otherwise detectsthe changes in the magnetic flux due to, for example, a topology of thetrack scale(s) 202S while utilizing magnetic flux densities that can beadjusted to operate within the linear range of the sensing member 803H.It is noted that the flux densities can be adjusted in the ferromagneticbridge circuit 901 by selecting the air gap CR1-CR2, VR reluctances.

As may be realized, in the aspects of the disclosed embodiment shown inFIGS. 8A-9C the portions of the ferromagnetic circuits (e.g. extensionmembers 823, 824 and at least corresponding portions of ferromagneticcircuit in FIGS. 9A-9C disposed in the sealed environment that includethe track air gap VR) that interface with the track 202 scale(s) 202Sacross the air aps 830, VR may include pick up features PIC (FIG. 9B)formed in or otherwise affixed to the ferromagnetic material of thecircuits. These pick up features PIC may be disposed on opposite sidesof the air gaps 830, VR and have a pitch substantially equal to thepitch P (FIG. 3) of a respective scale 202S and a size on the same orderof magnitude as the ferromagnetic features 202SE of the scale 202S suchthat local flux are established that are capable of sensing the track202 profile. These flux lines will add up and propagate to the sensingmember 803H such that the result of the flux across the sensor air gap810, 905 is substantially uniform for any given position of the track202. As can be seen in FIG. 9B when the pick up features PIC aresubstantially aligned with the ferromagnetic features 202SE of the scale202S substantially zero or no flux passes through the air gap 830, VR.When the pick up features PIC are misaligned with the ferromagneticfeatures 202SE of the scale 202S magnetic flux flows through the air gap830, VR such that movement of the ferromagnetic features 202SE acrossthe pick up features PIC produces a sinusoidal wave (as shown in FIG.9D) that is detected by the sensing member 803H.

Referring now to FIGS. 10A-10C, a portion of a sensor 203′″ isillustrated in accordance with an aspect of the disclosed embodiment.The sensor 203′″ may be substantially similar to sensor 203″ however, inthis aspect the bridge member BR′ includes flux concentrators FC1, FC2configured to maximize the magnetic flux that flows betweenferromagnetic circuit member 910′ and ferromagnetic circuit member 911′such that the sensing member 803H is disposed across or at least partlywithin the sensor air gap 905 defined by the flux concentrators FC1,FC2. Also, in this aspect, the ferromagnetic circuit members 910′, 911′are illustrated without the constant reluctance air gaps CR1-CR3 but inother aspects the ferromagnetic circuit members 910′, 911′ may includethe constant reluctance air gaps CR1-CR3 in a manner substantiallysimilar to that described above. As can also be seen in FIGS. 10A-10C anisolation wall may be disposed in a wall gap WG in a mannersubstantially similar to that described above with respect to FIGS.8A-9C. In operation each ferromagnetic circuit member 910′, 911′ has acorresponding magnetic flux Φ₁ and Φ₂ associated therewith. In a mannersubstantially similar to that described above, as the track 202 moveswithin the air gap VR the ferromagnetic features 202SE of the track 202move past the pick up features PIC of ferromagnetic circuit member 911′such that an air gap between the ferromagnetic features 202SE and thepick up features PIC changes as shown in FIGS. 10B and 10C. As can beseen in FIG. 10B when the pick up features PIC are substantially alignedwith the ferromagnetic features 202SE of the scale 202S the effectiveair gap between the puck up features PIC and the track 202 is at itsminimum value such that the fluxes Φ₁ and Φ₂ are substantially equal andsubstantially zero or no flux passes through the air gap VR and there issubstantially no magnetic flux across the air gap 905. When the pick upfeatures PIC are misaligned with the ferromagnetic features 202SE of thescale 202S the effective air gap between the pick up features PIC andthe tack 202 can be brought to is maximum such that the reluctanceacross the air gap VR is higher than the reluctance across the air gapVR when the pick up features PIC are substantially aligned with theferromagnetic features 202SE of the track 202 which causes a fluximbalance between the ferromagnetic circuit members 910′, 911′. As aresult of the flux imbalance between the ferromagnetic circuit members910′, 911′ a magnetic flux flows through the air gap VR and as a resulta flux Φ₃ (detected or otherwise sensed by the sensing member 803H)flows across the sensor air gap 905. As may be realized, movement of theferromagnetic features 202SE across the pick up features PIC causes theflux Φ₃ to change between maximum and minimum values such that the fluxΦ₃ emulates a sinusoidal wave (e.g. as shown in FIG. 9D) that isdetected by the sensing member 803H.

It is noted that the fluxes Φ₁ and Φ₂ can be adjusted in any suitablemanner to balance the fluxes of the ferromagnetic circuit members 910′,911 such as by adjusting a size of the wall gap WG (e.g. a DC offset) ofat least one of the ferromagnetic circuit members 910′, 911′ and/or thesize of the sensor air gap 905 (e.g. a signal amplitude) as shown inFIG. 10D. As may be realized, the air gap 905 across the sensing member803H may dictate an amount of maximum flux detected during points ofmisalignment between the pick up features PIC and the ferromagneticfeatures 202SE. It is also possible to induce a DC component of themagnetic flux by causing a constant imbalance between the ferromagneticcircuit members 910′, 911′ by altering the wall gap WG across theisolation wall of only one of the ferromagnetic circuit members 910′,911′.

As may be realized, more than one sensor as shown in FIGS. 8A-9C and10A-10D can be integrated with or otherwise mounted to the printedcircuit board 310 in a manner substantially similar to that describedabove. As can be seen in FIG. 11 a sensor configuration is illustratedthat is substantially similar to that described above with respect toFIGS. 5A, 6A-6C where the sensor track 202 includes a master scale 202S1(e.g. that may generate a sine wave), a Nonius scale 202S2 (e.g. thatmay generate any suitable reference wave form) and a segment scale 202S3(e.g. that may generate a cosine wave) where the master and segmentscales are measured with reference to the Nonius scale. Correspondingferromagnetic circuit members 1101-1103 (which may be substantiallysimilar to one or more of the ferromagnetic circuit members describedabove with respect to FIGS. 8A-9C and 10A-10D) are integrated with orotherwise mounted to the printed circuit board 310 for interfacing witha respective one of the scales 202S1-202S3 such that the sensing member803H is disposed adjacent a respective coil(s) 600 (FIGS. 5A and 7A-7D)for hysteresis compensation as described above. The signals from each ofthe sensing members of the ferromagnetic circuit members 1101-1103 maybe processed as described above to determine the position of the track202 and hence the robot drive 200 and/or arm(s) 208 connected to therobot drive.

As may be realized the aspects of the disclosed embodiment describedabove provide a position sensor that is capable of true absoluteposition measurement/feedback and for which no electronic components,cables or magnets are located in the sealed environment. As such thereis no need for hermetically sealed connectors via feed-throughs in theisolation wall 204. As may also be realized, the aspects of the positionsensor described herein provide for operation of the position sensor ina harsh environment (e.g. corrosive, extreme temperatures, highpressure, high vacuum, liquid media, etc.). The aspects of the positionsensor described herein also provide for operation of the positionsensor in the presence of contaminants (e.g. due to the magneticprinciples on which the position sensor operates—as described above)that may otherwise prevent reading the scales 202S of the track 202 suchas in the case of an optical sensor.

In accordance with one or more aspects of the disclosed embodiment, atransport apparatus includes a housing; a drive mounted to the housing;at least one transport arm connected to the drive, the drive includingat least one rotor having at least one salient pole of magneticpermeable material and disposed in an isolated environment, at least onestator having at least one salient pole with corresponding coil unitsand disposed outside the isolated environment where the at least onesalient pole of the at least one stator the at least one salient pole ofthe rotor form a closed magnetic flux circuit between the at least onerotor and the at least one stator, and at least one seal partitionconfigured to isolate the isolated environment; and at least one sensor,the at least one sensor including a magnetic sensor member connected tothe housing, at least one sensor track connected to the at least onerotor where the at least one seal partition is disposed between andseparates the magnetic sensor member and the at least one sensor trackso that the at least one sensor track is disposed in the isolatedenvironment and the magnetic sensor member is disposed outside theisolated environment.

In accordance with one or more aspects of the disclosed embodiment, atleast a portion of the at least one seal partition is integral to themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor comprises at least one ferromagnetic flux loophaving a sensor air gap where the magnetic sensor member interfaces withthe at least one ferromagnetic flux loop.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member is configured to detect changes in a reluctanceof the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop comprises first and secondferromagnetic flux loops having a sensor bridge member between the firstand second ferromagnetic flux loops where the sensor air gap is locatedin the sensor bridge member, one of the first and second ferromagneticflux loops having a track air gap in which at least a portion of the atleast one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop emulates a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, eachof the at least one ferromagnetic flux loop includes a track interfaceportion disposed in the isolated environment and a sensor memberinterface portion disposed outside the isolated environment, the trackinterface portion and the sensor member interface portion beingseparated by the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes flux concentrator elementsdisposed in the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes a track air gap in whichat least a portion of the at least one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor includes a substantially featureless trackinterface.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor track includes a first track having a first pitchand at least a second track having a respective pitch that is differentthan at least the first pitch, and the at least one sensor includes afirst sensor corresponding to the first track and at least a secondsensor corresponding to a respective one of the at least second track.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member comprises a differential sensor having sensorelements arranged to substantially match a pitch of the at least onesensor track such that differential sine and cosine output signals areobtained from the magnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements form a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements are disposed on a common printed circuit board of themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor interfaces substantially directly with the at leastone sensor track through the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, atransport apparatus includes a housing; a drive mounted to the housing;at least one transport arm connected to the drive, the drive includingat least one rotor having at least one salient pole of magneticpermeable material and disposed in an isolated environment, at least onestator having at least one salient pole with corresponding coil unitsand disposed outside the isolated environment where the at least onesalient pole of the at least one stator the at least one salient pole ofthe rotor form a closed magnetic flux circuit between the at least onerotor and the at least one stator, and at least one seal partitionconfigured to isolate the isolated environment; at least one sensor, theat least one sensor including a magnetic sensor member connected to thehousing, at least one sensor track connected to the at least one rotorwhere the at least one seal partition is disposed between and separatesthe magnetic sensor member and the at least one sensor track so that theat least one sensor track is disposed in the isolated environment andthe magnetic sensor member is disposed outside the isolated environment;and a sensor controller configured to generate sensor signal commands tothe at least one sensor based on sensor signals received from the atleast one sensor, where the sensor signal commands effect a change in atleast a predetermined characteristic of the sensor signals.

In accordance with one or more aspects of the disclosed embodiment, atleast a portion of the at least one seal partition is integral to themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor comprises at least one ferromagnetic flux loophaving a sensor air gap where the magnetic sensor member interfaces withthe ferromagnetic flux loop.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member is configured to detect changes in a reluctanceof the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop comprises first and secondferromagnetic flux loops having a sensor bridge member between the firstand second ferromagnetic flux loops where the sensor air gap is locatedin the sensor bridge member, one of the first and second ferromagneticflux loops having a track air gap in which at least a portion of the atleast one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop emulates a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, eachof the at least one ferromagnetic flux loop includes a track interfaceportion disposed in the isolated environment and a sensor memberinterface portion disposed outside the isolated environment, the trackinterface portion and the sensor member interface portion beingseparated by the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment,wherein the at least one ferromagnetic flux loop includes fluxconcentrator elements disposed in the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes a track air gap in whichat least a portion of the at least one sensor track is disposed

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor includes a substantially featureless track interface

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor track includes a first track having a first pitchand at least a second track having a respective pitch that is differentthan at least the first pitch, and the at least one sensor includes afirst sensor corresponding to the first track and at least a secondsensor corresponding to a respective one of the at least second track.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member comprises a differential sensor having sensorelements arranged to substantially match a pitch of the at least onesensor track such that differential sine and cosine output signals areobtained from the magnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements form a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements are disposed on a common printed circuit board of themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor interfaces substantially directly with the at leastone sensor track through the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, atransport apparatus includes a housing; a drive mounted to the housing;at least one transport arm connected to the drive, the drive includingat least one rotor having at least one salient pole of magneticpermeable material and disposed in an isolated environment, at least onestator having at least one salient pole with corresponding coil unitsand disposed outside the isolated environment where the at least onesalient pole of the at least one stator the at least one salient pole ofthe rotor form a closed magnetic flux circuit between the at least onerotor and the at least one stator, and at least one seal partitionconfigured to isolate the isolated environment; at least one sensor, theat least one sensor including a magnetic sensor member connected to thehousing, at least one sensor track connected to the at least one rotorwhere the at least one seal partition is disposed between and separatesthe magnetic sensor member and the at least one sensor track so that theat least one sensor track is disposed in the isolated environment andthe magnetic sensor member is disposed outside the isolated environment;a sensor controller communicably connected to the at least one sensor,the sensor controller being configured to provide sensor signalcommands; and a motion controller communicably connected to the at leastone sensor and the sensor controller and configured to receive sensorsignals from the at least one sensor, where the sensor controller isconfigured to control a change in at least a predeterminedcharacteristic of the sensor signals in response to communications fromthe motion controller.

In accordance with one or more aspects of the disclosed embodiment, atleast a portion of the at least one seal partition is integral to themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor comprises at least one ferromagnetic flux loophaving a sensor air gap where the magnetic sensor member interfaces withthe ferromagnetic flux loop.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member is configured to detect changes in a reluctanceof the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop comprises first and secondferromagnetic flux loops having a sensor bridge member between the firstand second ferromagnetic flux loops where the sensor air gap is locatedin the sensor bridge member, one of the first and second ferromagneticflux loops having a track air gap in which at least a portion of the atleast one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop emulates a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, eachof the at least one ferromagnetic flux loop includes a track interfaceportion disposed in the isolated environment and a sensor memberinterface portion disposed outside the isolated environment, the trackinterface portion and the sensor member interface portion beingseparated by the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes flux concentrator elementsdisposed in the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes a track air gap in whichat least a portion of the at least one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor includes a substantially featureless trackinterface.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor track includes a first track having a first pitchand at least a second track having a respective pitch that is differentthan at least the first pitch, and the at least one sensor includes afirst sensor corresponding to the first track and at least a secondsensor corresponding to a respective one of the at least second track.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member comprises a differential sensor having sensorelements arranged to substantially match a pitch of the at least onesensor track such that differential sine and cosine output signals areobtained from the magnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements form a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements are disposed on a common printed circuit board of themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor interfaces substantially directly with the at leastone sensor track through the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, atransport apparatus includes a housing; a drive mounted to the housing;at least one transport arm connected to the drive, the drive includingat least one rotor having at least one salient pole of magneticpermeable material and disposed in an isolated environment, at least onestator having at least one salient pole with corresponding coil unitsand disposed outside the isolated environment where the at least onesalient pole of the at least one stator the at least one salient pole ofthe rotor form a closed magnetic flux circuit between the at least onerotor and the at least one stator, and at least one seal partitionconfigured to isolate the isolated environment; at least one sensor, theat least one sensor including a magnetic sensor member connected to thehousing, at least one sensor track connected to the at least one rotorwhere the at least one seal partition is disposed between and separatesthe magnetic sensor member and the at least one sensor track so that theat least one sensor track is disposed in the isolated environment andthe magnetic sensor member is disposed outside the isolated environment;and a sensor controller configured for real-time sensor signal tuning inresponse to variations in at least one of an ambient condition of the atleast one sensor or state condition of the at least one sensor.

In accordance with one or more aspects of the disclosed embodiment, theambient condition of the at least one sensor is a temperature of the atleast one sensor.

In accordance with one or more aspects of the disclosed embodiment, thestate condition of the at least one sensor is at least one of a rotationdirection of the at least one sensor track or sensor hysteresis.

In accordance with one or more aspects of the disclosed embodiment,wherein at least a portion of the at least one seal partition isintegral to the magnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor comprises at least one ferromagnetic flux loophaving a sensor air gap where the magnetic sensor member interfaces withthe at least one ferromagnetic flux loop.

In accordance with one or more aspects of the disclosed embodiment, themagnetic member is configured to detect changes in a reluctance of thesensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop comprises first and secondferromagnetic flux loops having a sensor bridge member between the firstand second ferromagnetic flux loops where the sensor air gap is locatedin the sensor bridge member, one of the first and second ferromagneticflux loops having a track air gap in which at least a portion of the atleast one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop emulates a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, eachof the at least one ferromagnetic flux loop includes a track interfaceportion disposed in the isolated environment and a sensor memberinterface portion disposed outside the isolated environment, the trackinterface portion and the sensor member interface portion beingseparated by the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes flux concentrator elementsdisposed in the sensor air gap.

In accordance with one or more aspects of the disclosed embodiment, theat least one ferromagnetic flux loop includes a track air gap in whichat least a portion of the at least one sensor track is disposed.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor includes a substantially featureless trackinterface.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor track includes a first track having a first pitchand at least a second track having a respective pitch that is differentthan at least the first pitch, and the at least one sensor includes afirst sensor corresponding to the first track and at least a secondsensor corresponding to a respective one of the at least second track.

In accordance with one or more aspects of the disclosed embodiment, themagnetic sensor member comprises a differential sensor having sensorelements arranged to substantially match a pitch of the at least onesensor track such that differential sine and cosine output signals areobtained from the magnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements form a Wheatstone bridge.

In accordance with one or more aspects of the disclosed embodiment, thesensor elements are disposed on a common printed circuit board of themagnetic sensor member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor interfaces substantially directly with the at leastone sensor track through the at least one seal partition.

In accordance with one or more aspects of the disclosed embodiment, atransport apparatus includes a frame; a drive section connected to theframe having at least one drive shaft; a transport arm movably mountedto the drive section and driven by the at least one drive shaft; and aposition feedback apparatus including at least one track mounted to arespective one of the at least one drive shaft, each of the at least onetrack having at least one scale disposed thereon, and at least one readhead corresponding to a respective track, the at least one read headincluding at least one sensor mounted to a common support member, the atleast one sensor being configured to sense a respective scale on therespective track, and at least one energizing coil integrally formedwith the support member.

In accordance with one or more aspects of the disclosed embodiment, theat least one energizing coil is configured to generate an energizingpulse through a respective sensor to substantially eliminate sensorhysteresis.

In accordance with one or more aspects of the disclosed embodiment, thetransport apparatus further includes a controller connected to the atleast one read head, the controller being configured to sample trackdata from the at least one sensor so that sampling occurs apredetermined time after the energizing pulse through the respectivesensor is generated.

In accordance with one or more aspects of the disclosed embodiment, theenergizing pulse saturates the sensor.

In accordance with one or more aspects of the disclosed embodiment, theat least one read head and the respective track are separated from oneanother by an isolation wall such that the respective track is disposedin a first environment and the at least one read head is disposed in asecond environment different than the first environment.

In accordance with one or more aspects of the disclosed embodiment, thefirst environment is a vacuum environment and the second environment isan atmospheric environment.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor includes a substantially featureless trackinterface.

In accordance with one or more aspects of the disclosed embodiment, theat least one scale includes a first scale having a first pitch and atleast a second scale having a respective pitch that is different from atleast the first pitch and the at least one sensor includes a firstsensor corresponding to the first scale and at least a second sensorcorresponding to a respective one of the at least second scale.

In accordance with one or more aspects of the disclosed embodiment, thefirst sensor and the at least second sensor are immovably fixed to thesupport member.

In accordance with one or more aspects of the disclosed embodiment, theat least one sensor comprises a giant magneto resistive sensor or anysuitable magnetic sensor.

In accordance with one or more aspects of the disclosed embodiment avariable reluctance motor assembly includes a casing having a drumstructure, a stator mounted within the drum structure, a rotor mountedwithin the drum structure and interfaced with the stator, a sensor trackconnected to the rotor, and a giant magneto resistive sensor mounted tothe casing, where the casing includes a common datum that forms a statorinterface surface configured to support the stator and position thestator and rotor relative to each other for effecting a predeterminedgap between the stator and rotor and configured to support the giantmagneto resistive sensor in a predetermined position relative to thecommon datum so as to effect a predetermined gap between the giantmagneto resistive sensor and sensor track, where the stator, rotor,giant magneto resistive sensor and sensor track are positioned relativeto and depend from the common datum.

In accordance with one or more aspects of the disclosed embodiment thevariable reluctance motor assembly further includes an isolation wall2403 supported by the stator such that the isolation wall is located ina predetermined position relative to the common datum and the rotor.

In accordance with one or more aspects of the disclosed the casing is amonolithic member that forms the drum structure and into which slots areformed for one or more of sensors, control boards and drive connectors.

In accordance with one or more aspects of the disclosed embodiment thecasing is an integral assembly formed by two or more hoop membersconnected to each other to form the drum structure.

In accordance with one or more aspects of the disclosed embodiment avariable reluctance motor casing includes an exterior surface, aninterior surface where the exterior and interior surfaces form a drumstructure, the interior surface including a common datum that forms astator interface surface configured to support a stator and position thestator and a rotor relative to each within the casing to effect apredetermined gap between the stator and rotor, and a sensor interfacesurface configured to support a giant magneto resistive sensor relativeto a sensor track connected to the rotor and effect a predetermined gapbetween the giant magneto resistive sensor and sensor track, where thesensor interface surface is positioned relative to the common datum sothat the stator, rotor and giant magneto resistive sensor are positionedfrom and supported by the common datum.

In accordance with one or more aspects of the disclosed embodiment theinterior surface includes a rotor interface surface positioned relativeto the common datum so that the stator and rotor are positioned from andsupported by the common datum.

In accordance with one or more aspects of the disclosed embodiment, thesensor interface surface is formed as a slot within the drum structure.

In accordance with one or more aspects of the disclosed embodiment, theslot is configured to house the sensor and a motor control board.

In accordance with one or more aspects of the disclosed the drumstructure is a monolithic member into which slots are formed for one ormore of sensors, control boards and drive connectors.

In accordance with one or more aspects of the disclosed embodiment thedrum structure is an integral assembly formed by two or more hoopmembers connected to each other.

It should be understood that the foregoing description is onlyillustrative of the aspects of the disclosed embodiment. Variousalternatives and modifications can be devised by those skilled in theart without departing from the aspects of the disclosed embodiment.Accordingly, the aspects of the disclosed embodiment are intended toembrace all such alternatives, modifications and variances that fallwithin the scope of the appended claims. Further, the mere fact thatdifferent features are recited in mutually different dependent orindependent claims does not indicate that a combination of thesefeatures cannot be advantageously used, such a combination remainingwithin the scope of the aspects of the invention.

What is claimed is:
 1. A transport apparatus comprising: a housing; avariable reluctance drive mounted to the housing; and at least onetransport arm connected to the variable reluctance drive; where thedrive includes at least one rotor having salient poles of magneticpermeable material and disposed in an isolated environment; at least onestator having salient pole structures each defining a salient pole withcorresponding coil units coiled around the respective salient polestructure and disposed outside the isolated environment where the atleast one salient pole of the at least one stator and the at least onesalient pole of the rotor form a closed magnetic flux circuit betweenthe at least one rotor and the at least one stator; at least one sealpartition configured to isolate the isolated environment where theclosed magnetic flux circuit passes through the at least one sealpartition; and at least one sensor including a magnetic sensor memberconnected to the housing; at least one sensor track connected to the atleast one rotor; where the at least one seal partition is disposedbetween and separates the magnetic sensor member and the at least onesensor track so that the at least one sensor track is disposed in theisolated environment and the magnetic sensor member is disposed outsidethe isolated environment.
 2. The transport apparatus of claim 1, whereinat least a portion of the at least one seal partition is integral to themagnetic sensor member.
 3. The transport apparatus of claim 1, whereinthe at least one sensor comprises at least one ferromagnetic flux loophaving a sensor air gap where the magnetic sensor member interfaces withthe at least one ferromagnetic flux loop.
 4. The transport apparatus ofclaim 3, wherein the magnetic sensor member is configured to detectchanges in a reluctance of the sensor air gap.
 5. The transportapparatus of claim 3, wherein the at least one ferromagnetic flux loopcomprises first and second ferromagnetic flux loops having a sensorbridge member between the first and second ferromagnetic flux loopswhere the sensor air gap is located in the sensor bridge member, one ofthe first and second ferromagnetic flux loops having a track air gap inwhich at least a portion of the at least one sensor track is disposed.6. The transport apparatus of claim 3, wherein each of the at least oneferromagnetic flux loop includes a track interface portion disposed inthe isolated environment and a sensor member interface portion disposedoutside the isolated environment, the track interface portion and thesensor member interface portion being separated by the at least one sealpartition.
 7. The transport apparatus of claim 3, wherein the at leastone ferromagnetic flux loop includes flux concentrator elements disposedin the sensor air gap.
 8. The transport apparatus of claim 3, whereinthe at least one ferromagnetic flux loop includes a track air gap inwhich at least a portion of the at least one sensor track is disposed.9. The transport apparatus of claim 1, wherein the at least one sensortrack includes a first track having a first pitch and at least a secondtrack having a respective pitch that is different than at least thefirst pitch, and the at least one sensor includes a first sensorcorresponding to the first track and at least a second sensorcorresponding to a respective one of the at least second track.
 10. Thetransport apparatus of claim 1, wherein the magnetic sensor membercomprises a differential sensor having sensor elements arranged tosubstantially match a pitch of the at least one sensor track such thatdifferential sine and cosine output signals are obtained from themagnetic sensor member.
 11. The transport apparatus of claim 10, whereinthe sensor elements form a Wheatstone bridge.
 12. The transportapparatus of claim 10, wherein the sensor elements are disposed on acommon printed circuit board of the magnetic sensor member.
 13. Thetransport apparatus of claim 1, wherein the at least one sensorinterfaces substantially directly with the at least one sensor trackthrough the at least one seal partition.
 14. The transport apparatus ofclaim 1, wherein, the variable reluctance drive being configured toeffect at least extension and retraction of the at least one transportarm.
 15. A method of operating a transport apparatus, the methodcomprising: providing at least one transport arm connected to a variablereluctance drive, where the drive includes: at least one rotor disposedin an isolated environment, at least one stator disposed outside theisolated environment where a closed magnetic flux circuit is formedbetween the at least one rotor and the at least one stator, and at leastone sensor including: a magnetic sensor member connected to the housingand disposed outside the isolated environment, and at least one sensortrack connected to the at least one rotor and disposed within theisolated environment; and generating, with a sensor controller, sensorsignal commands to the at least one sensor based on sensor signalsreceived from the at least one sensor, where the sensor signal commandseffect a change in at least a predetermined characteristic of the sensorsignals.
 16. The method of claim 15, wherein the isolated environment isisolated by at least one seal partition and at least a portion of the atleast one seal partition is integral to the magnetic sensor member. 17.The method of claim 16, wherein the at least one sensor interfacessubstantially directly with the at least one sensor track through the atleast one seal partition.
 18. The method of claim 15, wherein themagnetic sensor member interfaces with a ferromagnetic flux loop of theat least one sensor within a sensor air gap of the ferromagnetic fluxloop.
 19. The method of claim 18, wherein each of the at least oneferromagnetic flux loop includes a track interface portion disposed inthe isolated environment and a sensor member interface portion disposedoutside the isolated environment, the track interface portion and thesensor member interface portion being separated by the at least one sealpartition.